1. Technical Field
The present application relates to an electrically operable, in one possible embodiment programmable hydrocephalus valve.
2. Background Information
Background information is for informational purposes only and does not necessarily admit that subsequently mentioned information and publications are prior art.
People suffering from hydrocephalus have the problem that an increased internal pressure on the brain resulting from excess cerebrospinal fluid (liquor cerebrospinalis) leads to serious problems for the persons concerned. The brain tissue thus becomes damaged and permanently broken down and different symptoms appear, such as dizziness, gait disorders, headaches, nausea, vomiting and dementia. If untreated, the disease can eventually be fatal. The nature and extent of the symptoms that arise depend on the underlying causes of the disease, the general constitution, but mainly on the age of the patient. In babies the pressure increase causes an unnatural growth of the head, in adults the brain substance disappears more quickly in favor of the water content inside the skull.
A successful treatment possibility for persons suffering from hydrocephalus has been available since the 1950s. An artificial drainage is implanted which enables the cerebrospinal fluid to drain away into other regions of the body, in which the diverted liquid can then be dissipated. The drainage can be controlled by means of valves that are intended to essentially ensure or promote the required and/or desired pressure inside the skull. Since then a plurality of various technical solutions have been proposed which extend the treatment possibilities or that are intended, however, to prevent or limit complications that frequently arise.
Various types of valve have been launched on the market up to now and can be sub-divided according to their functional principle as follows:
permanentadjustable1. Differential pressure valvesa: Silicone slit valve✓xb: Membrane valve✓xc: Ball-in-cone valve✓✓2. Hydrostatic valvesa: Anti-siphon valve✓xb. Liquid control✓xc: Gravitational valve✓✓✓ = availablex = not available
The rigid differential pressure valve of group 1 can be proposed as a silicone slit valve, as a membrane valve or as a ball-in-cone construction (U.S. Pat. No. 5,069,663, DE 30 20 991, US 20100010415). The valves in their opening characteristics are developed for the supine position of the patient. In the standing position these valves systematically lead to over-drainage, i.e. to un-physiologically low negative pressure in the head of the patient and can lead to severe complications. Valves with a complicated construction for the differential pressure and which fulfil their function in both the supine and standing position have as yet been unable to find any practical application (DE102009009880). A fundamental improvement in the characteristics of differential pressure valves results from the possibility of being able to percutaneously control the opening characteristics (U.S. Pat. No. 4,772,257, EP 0421557 A2, U.S. Pat. No. 5,928,182, EP 135991 A1, G8 2143008 A, U.S. Pat. No. 4,551,128, EP 0060369). In an enhancement of this, approaches are known, in which the adjustment can be electrically driven and supported by the use of sensors (EP2008683). The adjustment enables the valve function to be individually matched to the specific patients. This possibility exists for valves of the group 1-c, although the dependence of the physical behavior in the drainage system on the position of the patient is not solved here either. If the valves are adjusted to a low opening pressure, this will indeed on the one hand favor the clinical result, on the other hand the danger of over-drainage in the standing position is simultaneously and/or substantially simultaneously dramatically increased. Conversely, the adjustment to a very high value can indeed reduce the danger of over-drainage, thereby strongly negatively influencing the desired clinical result, as the now required and/or desired opening pressure in the supine position will be significantly too high.
Valves of the second group redress this. Hydrostatic valves are configured to take into account the changes in the physical conditions in the drainage system brought about by a positional shift. Three different principles are used for this.
The oldest design was realized in the “anti-siphon device”. Up to now a plurality of different designs based on the same principle have been commercialized (EP 0670740 B1, U.S. Pat. No. 5,800,376, DE 27 52 087). The effect of the negative pressure on the outlet of the valve is systematically minimized by this means. However, this feature is offset by the serious drawback that the subcutaneous pressure around the valve housing exercises a considerable influence on the mode of operation of the valve. Tissue growth or an unfavorable position of the patient can cause this pressure to vary considerably and even lead to the valve closing completely or substantially completely. These valves have also been unable to supersede the conventional valves (Drake, Toronto).
The same is true for the principle of flow control. Flow-regulating valves are intended to essentially ensure and/or promote that the drainage rate is held constant or substantially constant independently of the differential pressure acting on the valve. Whereas the drainage rate in conventional valves increases in proportion to the acting pressure differential, this is essentially prevented and/or minimized in flow-regulating valves (Siphonguard [Codman], Orbis Sigma Valve [Cordis], Diamond Valve [Phoenix]; EP 798012 A1, U.S. Pat. No. 4,627,832, U.S. Pat. No. 4,776,838). The average natural production of liquor is 23 ml/h. In practice, flow-regulating systems have the following problems:                Up to now it has been technically impossible to essentially ensure and/or promote the permissible drainage rate value. Variances in the context of the production process remain too large (Aschoff, Schoener).        The natural variance of production remains systematically ignored. If the individual values are too high or too low, then this can lead to over-drainage as well as to under-drainage.        The flow regulation is controlled by extremely small cross sections on the opening mechanism. Particles in the liquor such as for example cellular components exert a dramatic effect on the function and can very easily block the valve up. International comparative studies have shown that this principle could not improve the treatment results of the hydrocephalus (Drake et al).        
The gravity assisted valves are offered on the market in two variants. In the first approach, the flow control is effected by gravitationally controlled switching of two valves arranged in parallel or substantially parallel (DE 4401422, DE 4307387). The design therefore sets up two different pressure situations in the ventricular system of the patient as a function of the patient's posture. In the second approach, the weight of balls is exploited in order to set up an opening pressure that is modifiable as a function of the body position (EP 0617975, EP 0115973, DE 19535637). A gravity valve that is equipped with a percutaneously adjustable gravitation unit has recently become available (WO 2005092424). For the first time the technology enables individual adjustments contingent on body growth or on the increase in peritoneal pressure
The function of the ventricular drainage for hydrocephalus comprises on the one hand in draining away cerebrospinal fluid so as to essentially prevent and/or minimize the pathological pressure increase, and on the other hand, however, an unwanted high drainage and the extremely negative pressure resulting therefrom should be similarly essentially prevented and/or minimized. In previously available valves, this has been attempted on the basis of a pressure differential valve. Depending on the design, other influential factors are the position of the patient, the subcutaneous pressure or the viscosity of the cerebrospinal fluid. The differential pressure between the ventricle of the cerebrum and drainage medium (atrium, free abdominal cavity) is determinant for the drainage. However, very different situations can now lead to an increased pressure difference between the ventricle of the cerebrum and drainage medium. It could be that a large amount of cerebrospinal fluid had been produced; however it may also simply be that an increased pressure rise may have been caused by a change in position from the horizontal to the vertical. In the first case a valve has to open or should open, in the second case this should not occur. However, for a differential pressure valve, the situation is identical in both cases. Gravitation valves offer the best options but also in this case they are unable to react to temporarily modified situations, such as for example abdominal cavity pressure. Clinically unsatisfactory results can be illustrated by both over- as well as under-drainage. It often remains to be seen whether an optimal treatment success could have been possible.
Although the described valve systems have been able to solve many problems, the following aspects remain unsolved:
1. Matching the valve characteristics to growth- or age-dependent changes or other changes in the physiological boundary conditions
2. Non-invasive, selective adjustment of the valve characteristics with different set points for differing body positions of the patient
3. Consistent or substantially consistent therapy of patients up to the removal of the drainage that has perhaps become superfluous
4. Appropriate adjustment of the liquor drainage to individual specificities
5. Previously offered solutions are exclusively based on the differential pressure principle. Other parameters that could likewise impact the meaningful control of the liquor drainage are not addressed
6. Intelligent, situation-dependent control of valve characteristics
7. Subsequent analyses of incidents. The explanation of the incidents generally remains at the level of assumptions.
To solve these various problems, approaches have been made that are intended to implement controls adapted to them with the help of new valve processes (DE 19915558, DE 19654990, DE 10233601, WO 2010066438).
Proven valve technologies include spring-loaded ball valves, whose spring is adjustable. Different mechanical devices can be used for the adjustment. One possible adjustment device is formed by a rotor that is rotatably arranged in the valve. The periphery of the rotor is provided with a sliding surface, on which the spring rests directly or indirectly, such that an adjustment of the rotor causes an adjustment of the spring (DE102005013720, DE102007059300).
Another known valve technology also uses a rotor to adjust the spring. However, the rotor does not have a curved outside surface but rather has surfaces like screw flights or screw threads, on which the spring slides. This surface is mostly stepped (U.S. Pat. No. 7,235,060, U.S. Pat. No. 7,559,912, US2010/0010415).
The rotor is mostly pre-set using magnets, wherein part of the magnets are arranged in the rotor and implanted with the valve under the skin of the patient and wherein the other part of the magnet is rotated on the head of the patient above the rotor. This causes the magnets of the rotor to turn with the rotor.
However, there are other known proposals for adjusting the rotor, for example with a drive motor or with an electromechanical actuator. In this regard, electric motors, magnets and linear drives are concerned (EP2008683).
The valve switch in known embodiments is therefore operated electromechanically, electromagnetically, but in another embodiment also by exploiting the properties of shape memory materials. Problems result here in energy consumption and in the generation of heat as well as in biocompatibility, thereby making the constructions very complex. As far as is known, a programmable valve has not been offered on the market.
The above-discussed embodiments of the present invention will be described further herein below. When the word “invention” or “embodiment of the invention” is used in this specification, the word “invention” or “embodiment of the invention” includes “inventions” or “embodiments of the invention”, that is the plural of “invention” or “embodiment of the invention”. By stating “invention” or “embodiment of the invention”, the Applicant does not in any way admit that the present application does not include more than one patentably and non-obviously distinct invention, and maintains that this application may include more than one patentably and non-obviously distinct invention. The Applicant hereby asserts that the disclosure of this application may include more than one invention, and, in the event that there is more than one invention, that these inventions may be patentable and non-obvious one with respect to the other.